SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c2b9d32c7e3f1d4026dc2f781313944629864d7c8699278dd8a3640a3d2044' 
  AND token = 'sTt+p56Iu8BB/711BwTTugT5wh5qY70Lry5G+z8J7v4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}